Extreme pressure lubricant compositions



23%,404 Patented June 18, 1957 EXTREME PRESSURE LUBRICANT Mii)SiTiN Harry Levin, Fishkill, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application November 30, 1953, Serial No. 395,317

Claims. (Cl. 25247.5)

This invention relates to lubricating compositions characterized by antioxidant properties, freedom from corrosion and exceptional extreme pressure and anti-wear properties. More particularly, this invention discloses a novel lubricant additive which imparts a number of desirable properties to lubricating compositions.

In a commonly-owned copending application, Serial No. 392,502, filed November 16, 1953, in the names of Herman D. Kluge and Thomas C. Roddy, Jr., it is disclosed that rhodanine and its S-hydrocarbon-substituted compounds impart excellent extreme pressure properties and protection against silver corrosion to lubricating compositions. The subject invention involves the discovery that S-alxylaminobenzylidenerhodanines, also identified as 5-alkylaminobenzylidene-2-thiono-4-keto-thiazolidines, impart extreme pressure properties and protection against silver corrosion to lubricatingcompositions.

The novel lubricating compositions of this invention comprise an oleaginous material having lubricating properties as the major component and a minor amount sufiicient to impart extreme pressure and anticorrosive properties thereto of a 5-alkylaminobenzylidenerhodanine compound of the general formula wherein R is either hydrogen or an aliphatic radical and R is an aliphatic radical; aliphatic radical includes both alkyl and alkenyl groups. The S-alkylaminobenzylidenerhodanine usually constitutes 0.01 to 2.0 percent of the total lubricating composition.

The increasing speeds and torques available in modern automotive equipment have caused increased bearing pressures and rigorous service conditions on the gear teeth of hypoid gears and on other instances of metal-on-metal contact. As a consequence, the extreme pressure requirements of lubricants have steadily risen and it has been necessary to incorporate extreme pressure agents in a great number of greases and lubricating oils. The most efiective extreme pressure agents known prior to the instant invention were of the active sulfur, active halogen or combined active sulfurhalogen type. Active sulfur extreme pressure compounds are exemplified by sulfurized fatty acids and organic disulfides; an example of an active chlorine agent is chlorinated paraffin Wax; combined active sulfur-chlorine agents are exemplified by sulfa-chlorinated sperm oil. These extreme pressure agents which require a concentration of about 3 to 15 percent of the total lubricant composition in order to silver bearings encountered in diesel engines and have displayed significant ability to combat the corrosive effects of active sulfur and active chlorine-type compounds.

Another outstanding property of the S-alkylaminobenzylidenerhodanines is their efiiectiveness in very small concentrations. In contrast with the 3 to 15 Weight percent concentration required for the display of extreme pressure properties by active sulfur and active chlorine compounds, the novel additives of this invention greatly enhance extreme pressure and anticorrosive properties of lubricants when present in concentrations as low as 0.1 to 1.0 weight percent.

Rhodanine is the common chemical name of 2-thiono- 4-ketothiazolidine, which has the following structural formula:

o=o NH moi io=s S Rhodanine compounds containing an alkylaminobenzylidene radical on the 5 position and used in the lubricant compositions of this invention are exemplified by the following: 5-p-dimethylaminobenzylidenerhodanine, 5 p methylaminobenzylidenerhodanine, 5 m dipropylaminobenzylidenerhodanine, 5-o-ethylaminobenzylidenerhodanine, 5-o-methylbutylaminobenzylidenerhodanine, 5-p-di-isobutylaminobenzylidenerhodanine, 5-mhexylaminobenzylidenerhodanine and S-p-di-l-butenylbenzylidenerhodanine.

It Will be noted that the amino group contains at least one alkyl substituent. The aliphatic substituents on the amino group may contain 1 to 15 or more carbon atoms, but normally contain 1 to 6 carbon atoms. As is evident from the foregoing list of compounds, alkylamino group can be meta, ortho or para to the methylene group attached to the 5 position on the rhodanine nucleus.

The incorporation of 5-alkylaminobenzylidenerhodanine compounds imparts exceptional extreme pressure properties as well as antioxidant and anticorrosive properties to both greases and lube oil compositions. The concentration of the additive in both greases and oils is usually within the 0.01 to 2.0 weight percent concentration range; in general, concentrations of rhodanine compounds in the upper portion of the cited range are used in grease compositions, whereas concentrations in the lower part of the prescribed limits are employed in lube oil compositions.

The oleaginous lubricating base can be a hydrocarbon mineral oil, a synthetic lubricating base or mixtures thereof. If a hydrocarbon mineral oil is the base, it is either a paraflin base or a naphthene base fraction which advantageously has undergone solvent refining to improve its lubricity and its viscosity-temperature relationships. For certain applications such as greases, straight vacuum distillate lube fractions that have not undergone extensive solvent refining are employed as the lubricating base in which 5-alkylaminobenzylidenerhodanines are incorporated. In general, it can be stated that a wide variety of lube oil fractions are contemplated for use in the lubricating compositions of this invention; for example, paraffin base and naphthene baselube oil fractions having SUS viscosity at F. between 50 and 5,000 may be used as the base oil in the compositions of this invention.

The synthetic lubricating bases are usually of the ester or ether type. High molecular weight, high boiling liquid aliphatic dicarboxylic acid esters possess excellent viscosity-temperature relationships and lubricating properties and are finding ever increasing utilization in lube oils and greases adapted for high and low temperature lubrication; esters of this type are used in the formulation of jet engine oils and of greases designed for low alcohol or an aliphatic monocarboxylic' acid in specified molariratios are also employed 'as'the synthetic lubricating base in the compositions'of this invention; polyesters of this type are described in U. S. 2,628,974. Polyesters formed by reaction of 'a mixture containing specified amounts of dipropylene glycol, sebacic acid and 2-ethylhexanol and of a mixture containing adipic acid, diethylene glycol and 2-ethylhexanoic acid illustrate this class of synthetic polyester lubricating bases.

Polyalkylene 'ethers as illustrated by polyglycols are also used as the lubricating base in the compositions of this invention. Polyethylene glycol, polypropylene glycol, polybutylene' g'lycols and mixed polyethylene-polypropylene glycols are examples of'this class of synthetic lubricating bases. i

The sulfur analogs of the above-described diesters, polyesters and polyalkylene ethers are also used in the formulation of the lubricating compositions of this invention. Dithioesters are exemplified by di-Z-ethylhexyl thiosebacate and di-n-octyl. thioadipate; polyethylene thioglycol is an example of the sulfur analogs of the polyalkylene glycols; sulfur analogs of polyesters are exemplified by the reaction product of adipic acid, thioglycol and 2-ethylhexyl mercaptan'.

The lubricant compositions containing 5-alkylaminobenzylidenerhodanines'have awide variety of applications.- Since these compounds impart anti-wear, excep tional extreme pressure, antioxidant and'anticorrosive properties to lubricant compositions even'when present in very small concentrations; the'lubricating compositions of thisinvention are designed for a vvide variety of uses.

A partial list of their usesis as follows: motor oils for lubrication of internal combustion auto engines, 'airplane oils, diesel oils, jet engine'oils' which are usually of'the' synthetic base variety, cutting oils,"grinding oils,"'cylinderf oils, hydraulic oi'ls, automatic transmission fluids and valve oils. Greases containing 5+alkylaminobenzylidenerhodanines find application aschaissis greases, ball and roller bearing grease, rail and flangelubricants, all types of gear lubricants, traction motorlubricants and'alltypes of bearing lubricants.

.5 alkyla'rninobenzylidenerhodanine compounds are compatible with a wide variety-of additives employed in the formulation of lube oils and greases. Inmost apand divalent alkaline earth metal salts of 'alkylphenols;

antioxidants as illustrated by phenothiazine and polyalkyl-substitute d' phenolsfcorrosion inhibitors such: as

su'lfurized 'terpe'nes; "anti-rust agents 'as illustratd' by alkenyl-succinic acids; extreme pressure agents as 'illus tratedby" aryl' phosphates, sulfurizedf'joi ls and fats, chlorinated hydrocarbons and su1fo-chlorinated hydro carbons and organic acids. In greases the most c ommoiii 7 additives; with 5 alkylaminobenayliderierhodanine compounds are associated are antioxidant and extreme pressure agents; antioxidants are exemplified by phenyl alphanaphthylamine; extreme pressure agents are similar to those employed in lube oils.

The effectiveness of 5-'alkylaminobenzylidcnerhodanine compounds in combating silver corrosion was demonstrated in the EMD corrosion test which is used to determine the corrosiveness of heavy duty lubricating oils toward silver metal." Thetest gives an indication whether the oil is suitable for use in EMD (Electromotive Division) diesel enginescontainingfsilver-plated wrist pin The EMD corrosion test is run by placing silver strips or silver-plated" wrist pin bushings in the 'sample of oil under test which is maintained with stirring at 300 R. P. M. at a temperature of 300 F. i2 F. The appearance and weight changes of the strips or bushings are determined periodically with 24 and 72 hours being the mostcommon test periods employed. If the'silver-plate'd wrist pin bushing, which has an approximate size of 3 x l" x .25. is. used, it is pretreated at a temperature of about 140? F. with acetic acid hydrogen peroxide solution comprising 3 parts glacial acetic acid and-1 part percent hydrogen peroxide solution to remove lead flashing from the surface. After complete removal of the leadsas determined by visual observation, the bushing is immersed in distilled water, dried, polished with steel wool, cleaned withlintless paper'and weighed. In

thefollowing tests, silver strips which have a surface area equivalent to that of exposed silver on the bushing, specifically, 3.50. x 0.75" x 0.005", were employed. With the silver strips, the acetic acid-hydrogen peroxide treatment is 'eliniinated'and the strip is directly polished with steel wool,"cleaned..with lintless paper and weighed to the nearestmg.

-'Inthe test,'all observations and weight changes are recorded; on the basis of. the observation and weight changes, the oil is rated according to the following classifications:

After 72 Hours Appearance Unchanged:

x 5 mg. wt. change 6-25 mg. wt. change Over 25 mg. wt. chan e Dlscoloration or non-scaly, non-flaking deposit on str -'-=Max. 5 mg. wt. change-;

6-25 mg. wt. change-.. Over 25 mg. wt. change Scaly or flaking deposit on strip.

OIODOM Chil If strips from duplicate tests do not fall in the same percent basic barium sulfonate, 0.75 percent zinc alkyl dithiophosphate, 0.3Tpercent barium alkyl dithiophosphate and 0.225 percent neutral terpene-PzSs reaction product' The additives used in the above composition are'wenf known lubricant additives, which are more particularly de s cribed as follows: Basic barium sulfonate designates products resulting from the reaction of petroleum sulfonic acids with barium hydroxide in suchproportions that the resulting'rnixture contains one free hydroxyl group. Divalent metal alkyl dithiophosphates, specifi-j cally,' 'zinc and barium alkyl dithiophosphates, are formed by neutralization of the reaction product of phosphorus penta sulfide and m onohydroxy alcohols, particularly lauryl alcohol, cyclohexanol and capryl alcohol, with an excess of powdered metal ormetal oxide. A neutral st is repeated and'the oil is'rated terpene-PzSs product is obtained by oxidation of the reaction product of P2S5 with a teipene such as pinene, limonene, terpinene, dipentene and mixtures thereof.

The effect of S-alkylaminobenzylidenerhodanine compounds on the silver corrosion properties of the above base oil is shown in Table I.

TABLE I EMD corrosion test (24 hr.)

Silver Wt. Silver Appear- Rating Change, ance Base oil .c 14 Blackitflaky de- 5 pos Base oil +0.25% 5-(p-dimethyl- 0 Black powdery 2 aminobenzylidene) rhodanine deposit. (filtered).

treme pressure and anticorrosive properties thereto of a 5-alkylaminobenzylidenerhodanine compound having the general formula wherein R is selected from the group consisting of hydrogen and an aliphatic radical and R is an aliphatic radical.

2. A lubricating composition as described in claim 1 in which said 5-alkylaminobenzylidenerhodanine comprises 0.01 to 2.0 percent of the total composition.

3. A lubricating composition as described in claim 1 in which said rhodanine compound is 5-p-dialkylaminobenzylidenerhodanine.

4. A lubricating composition according to claim 1 in which the aliphatic radicals desginated by R and R contain 1 to 6 carbon atoms.

5. A lubricant composition according to claim 1 in which said rhodanine compound is S-(p-dimethylaminobenzylidene) rhodanine.

Loane Apr. 11, 1939 Lincoln et al. Sept. 3, 1940 

1. A LUBRICATING COMPOSITION COMPRISING A MINERAL LUBRICATING OIL HAVING LUBRICATING PROPERTIES AS THE MAJOR COMPONENT AND A MINOR AMOUNT SUFFICIENT TO IMPART EXTREME PRESSURE AND ANTICORROSIVE PROPERTIES THERETO OF A 5-ALKYLAMINOBENXYLIDENERHODANINE COMPOUND HAVING THE GENERAL FORMULA 